The Moon and Mercury will make a close approach, passing within a mere 12.3 arcminutes of each other. From some parts of the world, the Moon will pass in front of Mercury, creating a lunar occultation. The Moon will be 1 days old.
From Cambridge however, the pair will not be observable – they will reach their highest point in the sky during daytime and will be no higher than 0° above the horizon at dusk.
The Moon will be at mag -8.4; and Mercury will be at mag -0.3. Both objects will lie in the constellation Libra.
They will be close enough to fit within the field of view of a telescope, but will also be visible to the naked eye or through a pair of binoculars.
At around the same time, the pair will also share the same right ascension – called a conjunction.
A graph of the angular separation between the Moon and Mercury around the time of closest approach is available here.
The positions of the pair at the moment of closest approach will be as follows:
| Object | Right Ascension | Declination | Constellation | Magnitude | Angular Size |
| The Moon | 14h25m40s | 15°21'S | Libra | -8.4 | 31'35"3 |
| Mercury | 14h25m30s | 15°33'S | Libra | -0.3 | 5"0 |
The coordinates above are given in J2000.0. The pair will be at an angular separation of 15° from the Sun, which is in Virgo at this time of year.
The sky on 17 Oct 2031
| The sky on 17 October 2031 | ||||||||||||||||||||||||||||||||||
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3% 1 day old |
All times shown in EDT.
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Warning
Never attempt to point a pair of binoculars or a telescope at an object close to the Sun. Doing so may result in immediate and permanent blindness.
Source
The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
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| 13 Nov 2031 | – Mercury at highest altitude in evening sky |
| 16 Dec 2031 | – Mercury at highest altitude in morning sky |
Image credit
The Moon in conjunction with Venus and Jupiter, with the Very Large Telescope in the foreground. Image © Y. Beletsky, ESO, 2009.